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The World Health Organization has released its first-ever guidelines on dementia, advising that people may lower their risk by exercising regularly, not smoking and eating a healthful, balanced diet. But the WHO added that vitamin supplements are unlikely to help and there is not enough evidence to suggest an active social life can stave off decline.

In a report released Tuesday titled “Risk Reduction of Cognitive Decline and Dementia,” the WHO predicted the number of people with dementia will triple to 152 million globally by 2050. Yet it emphasized that dementia is not a natural or inevitable consequence of aging and may be prevented or delayed with various lifestyle changes.

“We have a huge burden that dementia poses, not only for people with dementia, but also for their [caregivers], as well as for countries and societies where there’s a huge economic impact,” said Neerja Chowdhary, a technical officer for the WHO’s department of mental health and substance abuse. “All this together, along with the fact … that currently we do not have a cure for dementia, makes it really imperative for us to focus on actually reducing the risk.”

Dr. Chowdhary noted the new guidelines were created to help member countries reach the targets they set out in a plan endorsed in 2017, the Global Action Plan on the Public Health Response to Dementia 2017-2025. The guidelines, aimed at health-care providers, policy-makers and the general public, are based on the latest available evidence, reviewed by a group of experts from around the world.

The WHO strongly recommends physical activity – at least 150 minutes per week of moderate aerobic exercise for those 65 and older – for those with normal cognition to reduce their risk of cognitive decline. Physical activity is also recommended – with the caveat that it may not be appropriate for everyone – for those with mild cognitive impairment.

Other strong recommendations include managing diabetes, offering cessation interventions to people who smoke and encouraging a “Mediterranean-like” diet that includes a high intake of fish, vegetables and legumes, and a low intake of meat and dairy.

The report, however, recommended against using dietary supplements, including vitamins B and E, polyunsaturated fatty acids and multisupplement complexes to reduce the risk of cognitive decline or dementia.

“There is really no evidence that suggests they are useful for cognitive decline or dementia,” Dr. Chowdhary said.

It gives a conditional recommendation to cognitive training – brain exercises designed to improve specific cognitive functions – though it states that the quality of evidence for such training is “very low to low.”

It also notes that while social support and participation are linked to good health and well-being throughout one’s life, there is insufficient evidence to suggest social activity reduces the risk of cognitive decline and dementia.

Many of the WHO’s recommendations are consistent with the messages provided by the Alzheimer Society of Canada, said Nalini Sen, director of the society’s research program. For instance, she said, lifestyle factors that are good for heart health are considered good for the brain.

However, Ms. Sen said, the two organizations differ when it comes to the benefits of social interaction. She said there is research to suggest regular social activity can reduce the risk of developing dementia and that social interactions can help those with dementia feel engaged and fulfilled, improving their quality of life.

Moreover, she pointed out that while people can reduce their risk of dementia with various lifestyle changes, risk factors such as one’s genes or age cannot be changed.

But just as it is not a certainty that people with risk factors will develop dementia, she said, "having little or no known exposure to risk factors cannot necessarily protect a person from developing the disease.”

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